Evidence for Intramolecular Permutation (Pseudorotation) at the Central Antimony Atom and Strong Equatophilicity of an Iron and a Ruthenium Ligand in Pentacoordinate Hypervalent Antimony Compounds

(2-Pyridyloxy)arsines as ligands in transition metal chemistry: a stepwise As(iii) → As(ii) → As(i) reduction

Neutral inherently tri- and tetradentate ligands of the type Ph_3-xAs(PyO)_x (x = 2 (1), 3 (2)) have been synthesized and characterized. Reaction of 1 with [RuCl₂(PPh₃)₃] affords complex [PhAs(μ-PyO)₂RuCl₂(PPh₃)] (3), whereas 2 and [RuCl₂(PPh₃)₃] react with formation of [As(μ-PyO)₂RuCl(PPh₃)₂] (5) and [Ph₃P(PyO)]Cl (6). Treatment of complex 5 with [AuCl(tht)] (tht = tetrahydrothiophene) results in liberation of tht and formation of [AuCl(As(PyO)₂)RuCl(PPh₃)₂] (7), featuring an (Au-As-Ru) core. For compounds 3, 5, and 7 the As-Ru and As-Au bond situation has been investigated using NBO, AIM and ELF analysis, allowing the assignment of pronounced canonical forms of σ-(As^III→Ru^II) to 3, σ-(As^II-Ru^I) to 5 and σ-(Au^I←As^I→Ru^II) to 7.

Sensing of aqueous fluoride anions by cationic stibine-palladium complexes

Turn on the lantern! The stibine donor ligand of a cationic palladium complex acts as a Lewis acid and reacts with a fluoride anion to afford the corresponding fluorostiboranyl-palladium species (see scheme). Bindung of the fluoride anion to the antimony center induces a change in denticity of the triphosphine unit and leads to a bright-orange trigonal-bipyramidal d(8) lantern complex.

Syntheses, Crystal and Solution Structures, Ligand-Exchange, and Ligand-Coupling Reactions of Mixed Pentaarylantimony Compounds

All possible combinations of mixed pentaarylantimony compounds bearing p-methylphenyl and p-trifluoromethylphenyl groups were synthesized; ArnTol5-nSb (n=0-5: Ar=p-CF3C6H4, Tol=p-CH3C6H4): Tol5Sb (1), ArTol4Sb (2), Ar2Tol3Sb (3), Ar3Tol2Sb (4), Ar4TolSb (5), and Ar5Sb (6). Compounds 2-5 are the first well-characterized examples of mixed acyclic pentaarylantimony species. The structures of 2-6 were determined by X-ray crystallography to feature trigonal-bipyramidal (TBP) geometry with the more electronegative p-trifluoromethylphenyl substituents selectively occupying the apical positions. Consideration of the chemical shifts of the ipso carbons of the aryl and tolyl groups suggested that the solution structures of 1-6 were also TBP, although their pseudorotation could not be frozen even at -80 degrees C. Ligand-exchange reactions (LERs) took place between 1 and 6 at approximately 60 degrees C in [D6]benzene and all six species 1-6 were found in the equilibrium mixture. The relative stabilities of 1-6 were determined quantitatively by comparison of the observed molar ratios of 1-6 in equilibrium with calculated statistical molar ratios, and Ar2Tol3Sb (3) was found to be the most stable. The ligand-coupling reactions (LCRs) of 2-5 in solution were greatly accelerated by adding Cu(acac)2 or Li+TFPB- (TFPB: [3,5-(CF3)2 C6H3]4 B), whereby the rate becomes comparable to the LER. The use of flash vacuum thermolysis (FVT) allowed the LCR to occur with very little ligand-exchange; the exception ArTol4Sb had very fast ligand-exchange. The selectivities of the LCRs were calculated from the yield of the biaryls synthesized by using FVT. These results were highly consistent with reactions catalyzed in solution, in which bitolyl was not obtained at all. The experimental results suggested that the LCR of pentaarylantimony compounds proceeds in the manner of apical-apical coupling.